He is 51 year old guy. That's mean that he was conceived between 1953 (coronation's time) to 1954 and born between 1954 to 1955. - On this time Princess Margaret was very busy person. So how she could be in pregnant and none saw that and gave a birth to any child
Photos month by month on getty (page 13 and next)
http://editorial.gettyimages.com/sou...%7c0&p=4&tag=2